ATM (Asynchronous Transfer Mode) that performs data communication by using fixed-length packets (or fixed-length frames) is widely used from an access network of a telecommunications carrier's network to a metro area network. ATM is a communication technology developed to handle various information items such as data, voice, and moving images over one network. In ATM, a fixed-length packet is referred to as an ATM cell.
ATM has standards such as AAL1 and AAL5. AAL1 is a communication standard of connection-type and fixed bit rate. AAL1 is primarily used for voice communication such as TDM. AAL5 is a communication standard of connectionless type and variable bit rate. AAL5 is used for data communication of Ethernet (registered trademark, hereinafter the same) and the like.
A method of for encapsulating and decapsulating data is different for AAL1 and AAL5. Therefore, in an ATM access network, an access accommodating apparatus that houses a user terminal is required for each of user's applications. For example, the ATM access network requires an ATM accommodating apparatus, an AAL1 accommodating apparatus, and an AAL5 accommodating apparatus.
In JP-A-2004-260238, a packet transfer apparatus that connects LAN and ATM is disclosed.